/*
 * Copyright 2010 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.websocket;

/**
 * Represents a WebSockets extension.
 */
public interface Extension {

  /**
   * Encode extension data into a byte array.
   * 
   * @param data
   * @return byte array containing encoding of extension data, or null if none
   */
  byte[] generateExtensionData(ExtensionData data);

  /**
   * @return the ID to use for this extension -- this is either a metadata ID
   * if {@link #usesMetadata()} returns true, or else an opcode.
   */
  int getId();

  /**
   * @return the registered name of this extension.
   */
  String getName();

  /**
   * Parse extension data.
   * 
   * @param bytes
   * @return an ExtensionData instance
   */
  ExtensionData parseExtensionData(byte[] bytes);
  
  /**
   * @return true if this extension uses metadata.
   */
  boolean usesMetadata();
}
